The Qiantang River Tidal Bore

Qiantang Tidal Bore in China (from: Youtube)

The Qiantang River runs for 459 km through Zhejiang, China, and flowing into the East China Sea via Hangzhou Bay. From Aug 15th to 21st in the Chinese Lunar Calendar, travelers come to Hangzhou Bay to see the largest tidal bore in the world, which can reach up to 9 meters in height and travel at up to 40 km/h.

The Cause of Tides (from: Wikipedia)

There are several reasons contributing to the spectacular tidal bore. First of all, from Aug 16th to 18th in the Chinese Lunar Calendar, the Sun, the Earth and the Moon are approximately in the same line. The gravitational forces of both the Sun and the Moon work together to create the greatest difference between high tide and low tide, which is called the spring tide.

In addition, the Qiantang River has a horn-shaped estuary, so the river surface suddenly becomes narrow when the water reaches the Hangzhou Bay. The abundance of sediment on the river bed slow down tides that come first, forcing waves behind to drive on those ahead. The prevailing southwest wind in coastal areas in China also helps speed up the tidal bores.

6 thoughts on “The Qiantang River Tidal Bore

  1. It’s really impressive how many different factors combine to produce such a massive bore tide by the time it reaches Hangzhou Bay.That seems like a pretty dangerous event to spectate! I noticed a lot of people very close to the river. Has anyone ever been hurt?


    1. Unfortunately, yes. Although the government has been warning of the danger, people still get hurt or even lose their lives when getting too close to the river. In 2013, a man got drowned while watching the tidal bore. But if the tourists follow the instructions and stay behind the safety line, they will be totally fine. Just don’t risk your life to test how close you can get to the tides!


  2. Before reading you blog, I had never heard of tidal bore before. It’s impressive how fast of speeds these waves can reach due to the strong differences in gravitational pulls from the Moon and Sun. Are there statistics or predictions on decreasing speeds or strengths on tidal bores due to the separation of the Moon and Earth this year?


    1. Sorry I didn’t find statistics for this year’s tidal bores. It seems that they haven’t published any information for 2019, but I believe updates would come out sometime in the summer. There definitely are differences between the strengths of the tidal bore each year, but the reason behind is a combination of changes in the climate, geographic condition and the influence of the Moon, which is hard to predict.


  3. This blog post was so interesting. I had no idea that the tides could cause these kinds of huge waves to come rushing in. I find it amazing that so many factors had to come together for this to happen, and yet they did and produced quite a spectacle. Your graphic was also very helpful for understanding how and when spring and neap tides happen.


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